The present invention relates to electrical control systems and more particularly to remote control systems for controlling electrical devices from a single or a plurality of remote stations.
Systems for controlling the startup and operation of electrical motors often require that the controlling functions be carried out at operating stations which are remote from the motors and their associated local controlling apparatus motor starters. Such operating stations may typically be up to about 1,000 feet or more away from the local controller apparatus which generally comprise a box enclosure containing high voltage power lines, contactors and relays, and include a switch mounted on the exterior thereof for selecting local or remote control operation. Conventionally, the remote control stations are "hard wired" to the local controller box by electrical conductor cable which adds substantially to the bulk and weight of the local controller box and accounts for a substantial portion of the installation cost of the system. In various applications, such as shipboard installations, the above-mentioned disadvantages become very significant, if not critical.
It is, therefore, an object of the present invention to provide a high reliability electrical control system which is of substantially reduced weight bulk.
It is a further object of the present invention to provide an electrical control system in accordance with the foregoing object which substantially eliminates EMI/RFI interference along the transmission channels thereof.
It is another object of the present invention to provide an electrical control system in accordance with the preceding objects which enables reduced installation costs.
It is yet another object of the present invention to provide a motor control system in accordance with the preceding objects which provides improved electrical isolation and eliminates electrical shock and spark/fire hazards.